Cake Boss star Buddy Valastro has noticeably lost weight recently, and now he’s sharing his new eating plan with fans.

Valastro posted a photo of himself alongside his wife, Lisa, on Instagram on Tuesday and revealed that he lost the weight on a special diet.

While many people applauded his weight-loss success, several admitted they had no idea what this diet actually is.

Optavia, according to the company’s website, is an eating plan that relies on what it calls “fuelings” to help people lose weight and maintain their weight loss. The company sells kits that include items such as peanut butter and chocolate chip bars, chocolate shakes, cranberry honey nut granola bars, roasted-garlic smashed potatoes, and rustic tomato herb penne. The diet takes people from eating almost strictly the company’s products (using five of them a day and having one regular meal) to a later approach of three meals and three products.

And it’s not cheap: The “Essential Optimal Kit (5&1)” costs $369.15 for a 30-day supply, while “essential fuelings,” which include variations of bars and shakes, cost $20.95 for seven servings.

Buddy “Cake Boss” Valastro in May. (Photo: Bobby Bank/Getty Images)

Clearly this works for Valastro, but it isn’t a plan that nutritionists are thrilled with.

“In general, I’m not a big fan of meal replacement shakes and bars because they don’t offer an education about how someone can sustain a healthy, balanced lifestyle that supports their goal,” New York dietician Jessica Cording tells Yahoo Lifestyle. However, she adds that she can see the appeal in the short term for someone who’s overwhelmed or doesn’t feel they’re ready for the educational component of weight loss. “Unfortunately, what I often see happen when people turn to meal replacement products or a plan that includes purchasing specific items is that, when they decide to go off the plan, they end up regaining whatever weight they lost,” she says.

The amount of calories that people consume on the eating plan also seems to be pretty low, even for a weight-loss diet, Beth Warren, founder of Beth Warren Nutrition and author of Secrets of aKosher Girl, tells Yahoo Lifestyle. And the plan’s reliance on getting people to eat the company’s own processed snack foods “makes the diet unrealistic to keep long term,” she says. Warren has personally worked with people who have come off of this diet and have had stomach upsets from the high amount of additive fibers, especially if they were dealing with a prior gastrointestinal issue, she says.

The diet also promotes very rapid weight loss, which usually causes muscle wasting and water loss, and it restricts exercise, likely because of the “inadequate amount of calories per day,” Warren says. “This isn’t a sustainable or healthy way to live,” she adds.

However, Gina Keatley, a nutritionist practicing in New York City, tells Yahoo Lifestyle that Optavia isn’t a “bad plan,” pointing out that there are worse options out there. Still, she says, dietitians try to keep people from forming a reliance on things like “fuelings” and supplements because these items are limited. On this eating plan, for example, you’re “going to be eating at least three fuelings every day … forever,” Keatley points out. Plus, most people tend to get stuck on the first step, where they eat prepackaged snacks all day, and then give up, she says.

Optavia spokesperson Erin Abney responds to thoughts on its program by telling Yahoo Lifestyle, “We know quick fixes don’t work. Optavia succeeds where other programs fail because it incorporates healthy habits into every aspect of the program, helping clients not only lose the weight, but inspire lashing change.” Average weight loss for clients on the Optimal Weight 5&1 Plan, with support, is 20 pounds, she adds, also noting that clients are in weight loss, on average, for 12 weeks.

Still, notes Warren, the best way to reach a weight and maintain it is to follow a plant-based diet using fresh, whole foods, lean proteins, fruits and vegetables, healthy fats, and quality carbohydrates, such as legumes and whole grains, which is also good for your health.

If you want to lose weight and aren’t sure where to start, Cording recommends being honest about your personal barriers to succeeding or making lifestyle changes stick. “There is so much information and so many products available out there that many people feel like they know what to eat and do, but the real struggle often comes in trying to apply that knowledge to their everyday life,” Cording says. This is where a dietitian could help someone get a handle on their situation and move forward, she says.

Ultimately, this is a diet that worked for Valastro, and he made it clear that it may not be for everyone. Still, it’s working for him!